1. Field of the Invention
The invention relates to a displacement pump for pumping pressure medium from a container to a consumer, in particular a servo-assisted steering system for motor vehicles. Inserted into the interior of the housing is a pump package, comprising a rotor, a cam ring, and a plurality of operating rods. By way of example, the operating rods may be embodied as vanes of a vane cell pump or as rollers of a roller cell pump. Between the cam ring and the rotor, work chambers are formed, which are subdivided by the operating rods and are bounded in the axial direction by control plates. A bypass flow limiting valve is used to regulate an effective flow. A throttle of the bypass flow limiting valve is formed by at least one bore. The throttle is embodied as a throttle insert, which to adjust a characteristic effective flow curve can be mounted in various positions between a pressure chamber of the pump and the bypass flow limiting valve.
2. Brief Description of the Prior Art
One such displacement pump is known from German Patent DE 24 02 017 C2 or U.S. Pat. No. 3,989,414. In this pump, a throttle insert is inserted into a pressure conduit transverse to the flow course. As a result, in the pressure conduit, a point of restricted cross section is formed. At this point the throttle bore discharges into the pressure conduit.
It has been found that this arrangement, under certain circumstances, reacts very sensitively to the rotary position of the throttle insert. Since the pressure conduit is a cast conduit that has a surface that is not entirely uniformly reproducable, the regulating characteristic curve of the flow regulating valve cannot be predetermined with the requisite precision.
The object of the invention is to achieve a more precise-tolerance characteristic curve of the flow regulating valve of a displacement pump.